Equal channel angular extrusion compaction of semi-amorphous Al85Ni10Y2.5La2.5 alloy powder

Al85Ni10Y2.5La2.5 alloy powder produced by gas atomization was compacted using equal channel angular extrusion (ECAE). The powder particle size was below 40 mum (-325 mesh grade), the powder was partially (similar to60%) amorphous and it contained intermetallic phases. Differential scanning calorimetry showed that crystallization of the amorphous phase starts at about 220 degreesC by precipitation of Al-based f.c.c. particles and continues at temperatures above 300 degreesC by formation of intermetallic phases. Four-pass B-C route compaction of the powder was conducted in a copper can at 280 degreesC, to avoid additional formation of intermetallic phases and retain some level of amorphicity of the compacted material. A non-homogeneous deformation of the compacted material during ECAE process was detected. The powder was completely consolidated and no voids were observed in the regions where powder particles were severely deformed. In other regions, non-deformed round particles, cracks, and high porosity were observed. Microstructural analysis showed that the severely deformed powder particles contained amorphous and/or f.c.c. phases only, while the non-deformed and/or fractured powder particles were fully crystalline and consisted mostly of intermetallic phases. (C) 2003 Elsevier B.V. All rights reserved.